The present invention found its origin in so-called masonry cavity-wall constructions. Masonry cavity walls have inner and outer vertical walls. The inner wall may be constructed from wood, with an inner surface of drywall, structural clay tile, vertical stacks of mortared bricks, or a shear concrete surface, as examples. The outer wall is generally constructed from vertical stacks of bricks that are held together by mortar. A space, or cavity, exists between the two walls, and the cavity may be partially filled with insulation. The space defining the cavity wall may be anywhere between 2 to 4.5 inches, as an example.
Typically, water may collect in the cavity between the inner and outer wall. To drain water within the masonry cavity wall, weep holes are commonly placed along the base of the outer wall. The weep holes allow water to pass from the cavity to drain outside the wall structure.
During construction of a masonry cavity wall, excess mortar and other debris can and does fall between the inner and outer wall. When the bricks are stacked during the erection of the outer wall, for example, mortar droppings are squeezed into the space between the walls. The excess mortar, as well as other debris, may drop to the base of the cavity and block the weep holes.
To prevent mortar or debris of any significant size from reaching and thus blocking a given weep hole, devices have been designed that can rest on the base of the wall cavity to cover and protect the weep holes, for instance. Such are shown in U.S. Pat. No. 5,230,189 and U.S. Pat. No. 5,343,661, as examples. As a further measure, a weep-vent wick may be placed within a weep hole itself to facilitate water removal. By preventing mortar and other debris from entering and thus blocking the weep holes, the devices facilitate the free flow of moisture from the cavity to the building exterior.
Although the mortar-net and weep-vent devices may prevent mortar and other debris from blocking the weep holes, such devices may be ineffective in preventing insects of an effective size from passing through the cavity-wall construction and thus entering the building. This may be an issue in particular for buildings such as hospitals and restaurants.